It is known that encapsulated semiconductor packages, that include a plastic encapsulation material as the package housing, are susceptible to cracking during solder reflow. This phenomenon is commonly referred to as the “popcorn effect” and often results in the failure of the package. This cracking is the result of the accumulation of moisture within the semiconductor package which, as the package is heated to a higher temperature during the solder reflow process, vaporizes, causing a build up of vapor pressure within the package resulting in cracking of the encapsulation material. The mismatch in the coefficients of thermal expansion between dissimilar materials of the package (e.g., a metallic leadframe and plastic encapsulation material) can also lead to the formation of cracks, and even complete delamination, at the interfaces between these materials. Moisture is able to accumulate in these cracks, which exacerbates the popcorn effect during solder reflow. The problem of cracking is more severe for so-called “green” packages, which use non-leaded solder that requires a higher solder reflow temperature of around 260° C. The problem of cracking is also more sever for so-called “robust” packages which are required to withstand more extreme operating conditions (e.g., packages for automotive applications).
A known way to address this problem of cracking is to provide an additional adhesion promotion coating on the encapsulated elements of the semiconductor package. However, the improvements which are observed as a result of the additional adhesion promotion coating are limited and further improvements are desired.